Concerns about global warming and environmental pollution caused by the use of fossil fuels in energy generation has resulted in a move towards so-called ‘green’ energy sources, or renewable energy sources such as tidal movement, wave power and wind power.
It has long been recognised that the waves in the sea and other bodies of water provide a vast and substantially untapped quantity of energy and many inventions have been made with the goal of achieving the aim of extracting power from the sea. One type of device for recovering wave energy is a downwards hanging flap or a pendulum which is reciprocally swung or rocked by waves in a caisson and the reciprocal movement of the pendulum is converted to electric power. Such an arrangement is described in U.S. Pat. No. 4,580,400. An alternative arrangement is a seabed mounted or supported structure having a hinged lever attached to a panel for reciprocation motion and such an arrangement is described in International Publication No. WO 2004/007953 A1. This arrangement is used in relatively deep water, at a preferred depth of about L/2, where L is the wavelength of the waves expected at the location of use. A somewhat similar arrangement is disclosed in WO 03/036081 where a reciprocating body is situated entirely underwater in a water basin of intermediate depth. In contrast an alternative device described in WO 98/17911 is for use in shallow waters. It makes use of the “translation” waves formed where deep-water waves break or are broken as they run up the seashore. The device has a flap, which is pushed backwards by the translation waves and returns to the upright between each wave impulse using springs.
There are numerous other examples of other wave power generating apparatus. Whilst such devices have been previously proposed they have fundamental failings for various reasons including lack of robustness in what is a very hostile environment; the need to ‘over engineer’ devices so as to make them suitable for use in hostile environments with consequent cost and maintenance implications; the need to utilise substantial anchorage devices for holding such apparatus in a secure manner on the seabed; and relatively substantial maintenance and repair costs for such devices.
In particular, previously proposed devices have generally been inefficient. The quantity of power captured from the incident waves has tended to be low and the subsequent conversion of the captured power into electricity poor. The devices have tended to produce power unevenly with large ‘spikes’ in the output, making it difficult to provide a smooth power output suitable for delivery into an electrical grid system.
It is an object of the present invention to avoid or minimise one or more of the foregoing disadvantages.